Why 300 blackout instead of 7.62x39?
- Thread starter kcub
- Start date
Its not just about case profile.
300blk has a cpl of use advantages as well.
1. It is more efficient out of short barrels
2. It works with heavy Subsonics without any changes to the gun. Shooting suoer sonic ammo... Do a mag change and shoot subs.
3. More bullet choices for the reloader. Just about any .308 cal bullet can be used, 762x39 bullets are much more limited in weights and profiles
4. The ability to get into a 300blkl gun by just changing the barrel on an already owned AR, makes it easy to "try out"
5. Availability of Quailty barrels, make it a real hunt capable ctg.
300blk has a cpl of use advantages as well.
1. It is more efficient out of short barrels
2. It works with heavy Subsonics without any changes to the gun. Shooting suoer sonic ammo... Do a mag change and shoot subs.
3. More bullet choices for the reloader. Just about any .308 cal bullet can be used, 762x39 bullets are much more limited in weights and profiles
4. The ability to get into a 300blkl gun by just changing the barrel on an already owned AR, makes it easy to "try out"
5. Availability of Quailty barrels, make it a real hunt capable ctg.
Because I like JD Jones better than Mikhail Kalashnikov!?
I've owned ARs in both, and prefer the .300 to the 7.62. I can share mags with my .223 and it gives up nothing in performance to the Russian round.
I don't shoot enough of either one to worry about ammo costs, quantity is what my 9mm and .223s are for.
In terms of quality soft-point factory ammo, there isn't that much difference in cost.
I've owned ARs in both, and prefer the .300 to the 7.62. I can share mags with my .223 and it gives up nothing in performance to the Russian round.
I don't shoot enough of either one to worry about ammo costs, quantity is what my 9mm and .223s are for.
In terms of quality soft-point factory ammo, there isn't that much difference in cost.
stagpanther
New member
I've found plenty of cheap remmie ammo at wally world. The remmie factory ammo is not especially accurate out of my 300 BO pistol--but the brass which is made by Barnes is great. You can also make your own brass fairy easily (I simply grind the case necks off to the shoulder and then resize and ream primer pockets where needed) out of spent 5.56, and I've found over-all it's easy to reload for and compared to other AR hybrids I've made it feeds and fires with wide tolerance towards a wide variation of configurations. It's a winner in my book.
Last edited:
A pause for the COZ
New member
I have both, like them both.
IMOP the 7.62x39 is a one trick pony. What you get in a box of purchased ammo is about it. not bad if thats all you want.
The 300 Black Out on the other hand is a master of many jobs.
If your intended role is with in 250 meters. The 300 Black Out has a load and configuration to give you the perfect medicine.
It has to be the best Suppressed SBR out there. Load up a 30 round mag of slow and heavy. I bet there is nothing better.
You can load just about any 30 cal bullet. from 100gr all the way up to 220gr whack masters. And every were in between. Even 30-30 bullets shoot good.
If you hand load it a breeze, by far the simplest round to reload for. Just about any fast rifle powder will do with just about any bullet.
Like I said have em both and like em both. But if it comes to a choice. I will be keeping my 300 Black out.
Actually I will be getting another one. I have a carbine, but I really want a SBR and a can to go with it.
Do like me and get them both.
IMOP the 7.62x39 is a one trick pony. What you get in a box of purchased ammo is about it. not bad if thats all you want.
The 300 Black Out on the other hand is a master of many jobs.
If your intended role is with in 250 meters. The 300 Black Out has a load and configuration to give you the perfect medicine.
It has to be the best Suppressed SBR out there. Load up a 30 round mag of slow and heavy. I bet there is nothing better.
You can load just about any 30 cal bullet. from 100gr all the way up to 220gr whack masters. And every were in between. Even 30-30 bullets shoot good.
If you hand load it a breeze, by far the simplest round to reload for. Just about any fast rifle powder will do with just about any bullet.
Like I said have em both and like em both. But if it comes to a choice. I will be keeping my 300 Black out.
Actually I will be getting another one. I have a carbine, but I really want a SBR and a can to go with it.
Do like me and get them both.
Last edited:
stagpanther
New member
I use mostly pistol powders with my supersonic reloads.
"I thought it was because 7.62X39 didn't feed very well in AR's, isn't it only the recent 7.62X39 AR's that work reliably?"
Really had/has little to do with the AR itself but everything to do with proper AR magazines.
"IMOP the 7.62x39 is a one trick pony. What you get in a box of purchased ammo is about it. not bad if thats all you want."
How do you figure? The 7.62x39 is not difficult to reload and bullets for varmint, medium game, and plinking are readily available.
"300 Blackout has the same case profile as 223 except that it's not necked down."
300AAC uses the 221 Fireball case necked up but it does still have a shoulder.
If you reload and like to tinker, the 300AAC is a lot of fun, cheap to load, and the most economical swap.
If you just want a 30(ish) cal carbine to shoot for fun and an occasional short range deer/coyote hunt w/o worrying about picking up your empty cases, the 7.62x39 is a better choice.
I have both calibers in AR's but I'm under no delusions of the mythical/mystical capabilities of the 300AAC. It does a couple of things better than other options but it's not magic.
Really had/has little to do with the AR itself but everything to do with proper AR magazines.
"IMOP the 7.62x39 is a one trick pony. What you get in a box of purchased ammo is about it. not bad if thats all you want."
How do you figure? The 7.62x39 is not difficult to reload and bullets for varmint, medium game, and plinking are readily available.
"300 Blackout has the same case profile as 223 except that it's not necked down."
300AAC uses the 221 Fireball case necked up but it does still have a shoulder.
If you reload and like to tinker, the 300AAC is a lot of fun, cheap to load, and the most economical swap.
If you just want a 30(ish) cal carbine to shoot for fun and an occasional short range deer/coyote hunt w/o worrying about picking up your empty cases, the 7.62x39 is a better choice.
I have both calibers in AR's but I'm under no delusions of the mythical/mystical capabilities of the 300AAC. It does a couple of things better than other options but it's not magic.
Also ... the casehead of the 7.62x39 barely fits in a AR15 bolt.
So the bolt is lacking a lot of material at the locking lugs.
That creates a weak point.... if it ( the 7.62x39 bolt ) breaks in the field... well you are out of luck.
If a 300 BO / 5.56 bolt breaks in the field, you will have a FAR better chance of finding one.
The 300 BO really only needs a different barrel.... everything else is OEM parts.
IMHO... the 300 BO is the best candidate for the conventional AR platform.
It is a very flexible / versatile cartridge.
It isn't everyone's cup o' tea and that's ok.
So the bolt is lacking a lot of material at the locking lugs.
That creates a weak point.... if it ( the 7.62x39 bolt ) breaks in the field... well you are out of luck.
If a 300 BO / 5.56 bolt breaks in the field, you will have a FAR better chance of finding one.
The 300 BO really only needs a different barrel.... everything else is OEM parts.
IMHO... the 300 BO is the best candidate for the conventional AR platform.
It is a very flexible / versatile cartridge.
It isn't everyone's cup o' tea and that's ok.
While there is a dozen or so different bullets to choose from in .311 there are DOZENS in .308 with a much broader weight range. Also try switching from a 110 grain bullet followed by a 240 grain bullet either suppressed or un suppressed and still get the gun to function without any modifications to it. Not happening with the x39
The .300bo uses .223/5.56 brass cut down. The .300Whisper used 221 Fireball. Sleight difference and the Whispers will chamber and shoot just fine in a .300bo but the .300bo will have problems chambering in a Whisper
"True, but, if the Emperor is in the middle of the forest, trips and falls, causing an AD that kills him and no one else is around to hear it, is he still naked?"
I am still laughing. I almost hurt myself.
Anyway, back to the subject.
I have made quite a few 300 Whispers on ARs and I have never made one or seen one that you could change the mag from loads at subsonic velocities to loads with supersonic ammo and have the rifle work.
It is a balancing act.
You see, if you have the full power recoil spring the subsonic loads will not compress it, so the gun short cycles. So when you go to the subsonic loads you need to change out the recoil spring. You need to change it back when you go to supersonic loads.
Next you will find that the reduced weight recoil spring will not strip rounds from a standard magazine because it is not strong enough. The easy answer is to use the 30 round Mag-Pul mags (they are quite slick) and load only 8-9 rounds . In most cases this is the easy fix to this problem.
Opening up the gas port and putting an adjustable gas manifold is helpful, but not a 100% cure because no matter how big you make the port, the gas still has to pass the tube and that tube is only as large as it is, so you can't get more gas than the tube will give you.
But the idea that an AR in 300 AAC is "just a swap from one type of ammo to the other" is not so, or if it is I have never seen it. If anyone out there knows of some carbines that will allow this I wouyld LOVE to talk to the makers and find out how they are doing it. But as I said, in the last 6 years or so since I have been making them, I have yet to see a gun that you can do this with.
I disagree that the 7.62X39 is not as reliable, but it is (or was) a problem in the early attempts because the 7.62 mags have to curve a LOT more then the 5.56 mags, but the part of the mag that inserts into the mag well has to be left straight. So making good reliable 7.62X39 mags for an AR is a trick. it is done by some manufacturers but others miss the mark sometimes.
All that is now different with some of the newer lower receivers made for the AR platform but designed to use the standard AK mags.
Some of the new lowers are excellent and they work like a charm with regular AK mags so the jamming we see in the earlier guns is not a problem as much today as it was 10 years ago.
However one bug that still bites now and then is the hammer fall of an AR VS an AK.
The hammer springs and the hammer itself on an AK is WAY larger and stronger than they are on ARs.
Surplus imported 7.62X39 has hard thick primers and we see a lot of miss-fires from some lots of ammo when you attempt to use them in ARs.
Nothing can be done to correct this. The strongest springs you can buy, combined with the GI hammer (the heaviest one you can get still will give you 1-2 clicks per mag in ARs.
ARs just are not as powerful in their hammer designs as AKs. So be aware of that if you are considering a 7.62X39 VS a 300 Whisper.
That is the only advantage I have ever seen of the 300 over the Russian shell.
However I must point out that in most cases 300 AAC/Whisper shooters fire handloads. If we compare things fairly "apples to apples", we must then also compare performance of handloads with brass case 7.62X39, with American primers, and at that point the argument for the 300 over the Russian falls apart. With American made primers the 7.62X39 works just fine in ARs
I am still laughing. I almost hurt myself.
Anyway, back to the subject.
I have made quite a few 300 Whispers on ARs and I have never made one or seen one that you could change the mag from loads at subsonic velocities to loads with supersonic ammo and have the rifle work.
It is a balancing act.
You see, if you have the full power recoil spring the subsonic loads will not compress it, so the gun short cycles. So when you go to the subsonic loads you need to change out the recoil spring. You need to change it back when you go to supersonic loads.
Next you will find that the reduced weight recoil spring will not strip rounds from a standard magazine because it is not strong enough. The easy answer is to use the 30 round Mag-Pul mags (they are quite slick) and load only 8-9 rounds . In most cases this is the easy fix to this problem.
Opening up the gas port and putting an adjustable gas manifold is helpful, but not a 100% cure because no matter how big you make the port, the gas still has to pass the tube and that tube is only as large as it is, so you can't get more gas than the tube will give you.
But the idea that an AR in 300 AAC is "just a swap from one type of ammo to the other" is not so, or if it is I have never seen it. If anyone out there knows of some carbines that will allow this I wouyld LOVE to talk to the makers and find out how they are doing it. But as I said, in the last 6 years or so since I have been making them, I have yet to see a gun that you can do this with.
I disagree that the 7.62X39 is not as reliable, but it is (or was) a problem in the early attempts because the 7.62 mags have to curve a LOT more then the 5.56 mags, but the part of the mag that inserts into the mag well has to be left straight. So making good reliable 7.62X39 mags for an AR is a trick. it is done by some manufacturers but others miss the mark sometimes.
All that is now different with some of the newer lower receivers made for the AR platform but designed to use the standard AK mags.
Some of the new lowers are excellent and they work like a charm with regular AK mags so the jamming we see in the earlier guns is not a problem as much today as it was 10 years ago.
However one bug that still bites now and then is the hammer fall of an AR VS an AK.
The hammer springs and the hammer itself on an AK is WAY larger and stronger than they are on ARs.
Surplus imported 7.62X39 has hard thick primers and we see a lot of miss-fires from some lots of ammo when you attempt to use them in ARs.
Nothing can be done to correct this. The strongest springs you can buy, combined with the GI hammer (the heaviest one you can get still will give you 1-2 clicks per mag in ARs.
ARs just are not as powerful in their hammer designs as AKs. So be aware of that if you are considering a 7.62X39 VS a 300 Whisper.
That is the only advantage I have ever seen of the 300 over the Russian shell.
However I must point out that in most cases 300 AAC/Whisper shooters fire handloads. If we compare things fairly "apples to apples", we must then also compare performance of handloads with brass case 7.62X39, with American primers, and at that point the argument for the 300 over the Russian falls apart. With American made primers the 7.62X39 works just fine in ARs
The AR design works poorly with cases that have too fat a rim or too much taper. The 5.56 case has a .378 rim, the SPC case has a .422 rim, and 7.62x39 has a .447 rim. It turns out that's a bit too much and causes problems both with the bolt assembly and with the magazine/feed system.
.300 BLK is simply an easy way to get a .30 cal in an AR-15 platform. The performance isn't that great, but the level of complexity is low compared to the better performing options.
.300 BLK is simply an easy way to get a .30 cal in an AR-15 platform. The performance isn't that great, but the level of complexity is low compared to the better performing options.
If you want 50% more power than 5.56, there are better choices, they have been on the market longer, and one is a military SBR round used in the Mid East.
.300BO was a market "sharing" concept by AAC to exploit sales of subsonic guns and silencers. They usurped .300 Whisper, which was a niche cartridge and barely moving on the market.
If anything, using it supersonic was returning it to it's roots as a workaround with 3Gun rules of the '80s that outlawed 5.56 in competition. Well, the .30x5.56 wildcats got tossed out to, as Real Men only shot .30 cal battle rifles back then. Once 5.56 was allowed, guess what. all those Real Men quickly switched to AR15's in 5.56 and moved on. .300 Whisper was developed later by SSK.
Now we get the consumer market involved, and as with ANY non military surplus cartridge, you decide to reload or buy surplus cheaper.
If all that is needed is to pop caps and poke holes in paper or dirt, shoot all the 5.56 or X39 you can get.
If you need a specific recipe of power and range to hit a target, then you specify it, sort out which rounds are the ones that provide it, and live with the choice. It will be the most effective, which strangely enough includes cost of ammo and whether the difference in downrange performance is just incremental. A lot of times the final choices are within 10%. Close enough.
For my AR pistol, I could have chosen 6.8 as I already had magazines galore, but I didn't - I picked 5.56 as the ammo is dirt cheap for plinking.
Enjoyed using it last fall in two hunting seasons as being a pistol it fit firearms and alternative weapons. I mention all that because too often the question comes up "X or Y?" when the real answer might be "Not X or Y" at all.
Frankly, since the run on .22 we get a lot of this, which is another factor. Since the question seems to be about ammo costs, then why pick an expensive commercial round which is likely not ever going to be available surplus? Don't mind me being critical about that, but a lot of us are still waiting for 25c a round 6.8. I chose not to wait as my performance task didn't "need" the extra power. I could use it, yes, but popping caps at targets with an AR takes a lot of cheap ammo to get skill levels up. And commercial loads aren't the ones to pick for that.
I could get 1,000 foot pounds of force out to 60-80 meter with 5.56 for deer hunting, which is a lot further than I can see in woodlands or dense brush where whitetail hide after leaf fall.
Instead of comparing .300 vs x39, spec what you need the ammo to do and then narrow the range of choices. Including costs I would suggest that good ol 5.56 could do the job.
.300BO was a market "sharing" concept by AAC to exploit sales of subsonic guns and silencers. They usurped .300 Whisper, which was a niche cartridge and barely moving on the market.
If anything, using it supersonic was returning it to it's roots as a workaround with 3Gun rules of the '80s that outlawed 5.56 in competition. Well, the .30x5.56 wildcats got tossed out to, as Real Men only shot .30 cal battle rifles back then. Once 5.56 was allowed, guess what. all those Real Men quickly switched to AR15's in 5.56 and moved on. .300 Whisper was developed later by SSK.
Now we get the consumer market involved, and as with ANY non military surplus cartridge, you decide to reload or buy surplus cheaper.
If all that is needed is to pop caps and poke holes in paper or dirt, shoot all the 5.56 or X39 you can get.
If you need a specific recipe of power and range to hit a target, then you specify it, sort out which rounds are the ones that provide it, and live with the choice. It will be the most effective, which strangely enough includes cost of ammo and whether the difference in downrange performance is just incremental. A lot of times the final choices are within 10%. Close enough.
For my AR pistol, I could have chosen 6.8 as I already had magazines galore, but I didn't - I picked 5.56 as the ammo is dirt cheap for plinking.
Enjoyed using it last fall in two hunting seasons as being a pistol it fit firearms and alternative weapons. I mention all that because too often the question comes up "X or Y?" when the real answer might be "Not X or Y" at all.
Frankly, since the run on .22 we get a lot of this, which is another factor. Since the question seems to be about ammo costs, then why pick an expensive commercial round which is likely not ever going to be available surplus? Don't mind me being critical about that, but a lot of us are still waiting for 25c a round 6.8. I chose not to wait as my performance task didn't "need" the extra power. I could use it, yes, but popping caps at targets with an AR takes a lot of cheap ammo to get skill levels up. And commercial loads aren't the ones to pick for that.
I could get 1,000 foot pounds of force out to 60-80 meter with 5.56 for deer hunting, which is a lot further than I can see in woodlands or dense brush where whitetail hide after leaf fall.
Instead of comparing .300 vs x39, spec what you need the ammo to do and then narrow the range of choices. Including costs I would suggest that good ol 5.56 could do the job.
Theohazard
New member
I don't have any personal experience with 300 Whisper and how much it differs in terms of pressure from 300 Blackout, but I have seen many 300 Blackout setups where you could switch from subsonic to supersonic without swapping any parts or even adjusting the gas, and they worked just fine.Wyosmith said:
With 300 Blackout, there are usually four different gas pressure levels depending on the ammo type used and whether you're running a silencer or not:
1) Suppressed with supersonic ammo.
2) Unsuppressed with supersonic ammo.
3) Suppressed with subsonic ammo.
4) Unsuppressed with subsonic ammo.
Most 300 Blackout rifles I've seen could be tuned to reliably run three of these (either 1 - 3 or 2 - 4) without any parts swap or gas adjustment needed. Most people choose to run 1 - 3 and don't worry that the rifle doesn't work on 4; most people who shoot 300 Blackout suppressed have no need to shoot subsonic ammo without their silencer attached. Or you can get an adjustable gas block and often that will let you run all 4.
At my old job I had a coworker who had a 9" AAC MPW pistol with an SDN-6 silencer that would run all 4 even without an adjustable gas block; it was overgassed on 1 and barely cycled on 4, but it worked. Personally, I'd rather just tune it to run 1 - 3 reliably instead of having it barely work on 1 and 4.